Method and apparatus for cryosurgery

ABSTRACT

The present invention pertains to an apparatus for cryosurgery. The apparatus comprises a cryoneedle having a diameter less than 3.2 mm. The apparatus is also comprised of a thermal insulation shell disposed about a portion of the cryoneedle for reduction of heat transfer from surrounding tissues or freezing prevention of surrounding tissues during application of the cryoneedle with the shell. The cryoneedle and shell are configured for insertion into a body of a patient. The present invention pertains to a method for freezing tissues. The method comprises the steps of bringing into contact a cryoneedle having a diameter of less than 3.2 mm with a patient&#39;s body. Next, there is the step of flowing the cryofluid through the cryoneedle.

This application is a continuation of application Ser. No. 08/688,692filed on Jun. 24, 1996 now U.S. Pat. No. 6,039,730.

FIELD OF THE INVENTION

The present invention is related to cryosurgery. More specifically, thepresent invention is related to a method and apparatus for cryosurgeryinvolving a cryoneedle having an outlet tube adjacent an inlet tube forcryofluid which cools the cryoneedle.

BACKGROUND OF THE INVENTION

This invention relates to minimally invasive cryosurgery. Moreparticularly, this invention concerns the structure and the method ofoperation of a cryosurgical apparatus, which consists of one or morecryoprobes and a pressurized cryofluid source.

Cryosurgery, or the destruction of undesired biological tissues byfreezing, has long been accepted as an important alternative techniqueof surgery (Orpwood, 1981; Rubinsky and Onik, 1991; Gage, 1992).Compared with conventional means of destroying tissues, such as surgicalexcision, radiotherapy and chemotherapy, visceral cryosurgery(especially minimal-invasive cryosurgery) offers the following potentialadvantages: simplicity of the procedure, minimal bleeding, anaestheticeffect of low temperatures, short period of patient recovery, low cost,minimal scarring, and possible stimulation of the body's immune system.

James Arnott, an English physician, was the first to introduce thetechnique of destruction of biological tissues by freezing in 1865.Since Arnott's first report, numerous cryodevices and techniques havebeen suggested. These have included pre-cooled metal blocks, spray/pourfreezing with compressed or liquefied applications, cryogenic heatpipes, Joule-Thompson effect based cryoprobes and boiling effect basedcryoprobes. However, as a result of the high cooling power usuallyneeded for cryosurgery, and especially of internal organs, the boilingeffect and the Joule-Thompson effect have been found to be thepreferable cooling technique by most cryosurgeons.

Minimally invasive cryosurgery is monitored by ultrasound, CT or MRI;however, ultrasound is the most accepted imaging technique amongcryosurgeons today. Utilizing these techniques, the cryosurgeon insertsthe cryoprobe(s) into the region to be cryotreated. Then, thecryosurgeon activates the cryoprobe(s) according to a cooling protocoland monitors the frozen region growth (which is also termed “ice-ball”).When the undesired tissues are completely frozen, or when there is adanger of cryodestruction to important surrounding tissues, thecryosurgeon terminates the cooling process and the thawing stagefollows. In some cases the cooling/thawing stages are repeated in orderto increase cryodestruction.

The application of minimal-invasive cryosurgery calls for: a cryoprobeinsertion technique that causes minimal damage to the surroundinghealthy tissues, an accurate localization of the cryoprobe tip, and aprecise monitoring of the frozen region formation. These criteria haveserved as the motivation for the continued efforts toward the reductionof cryoprobe diameter and improvement in imaging techniques. Ultimately,the cryoprobe diameter is a result of the diameter of the cryofluidtubes and by the cryoprobe's thermal insulator thickness. Since atypical cryoprobe diameter is relatively large, a pathway must beprovide for the cryoprobe into the cryotreated region. An alternativesolution for this problem is given by the invention presented hereby.

SUMMARY OF THE INVENTION

The objective of the invention is to provide a method and apparatus forminimal-invasive cryosurgery. More particularly, the objective of theinvention is to provide a method and a cryoprobe that minimize thedamage caused to the surrounding tissues due to either preparations forthe cryoprocedure or cryoprobe penetration.

Another objective of the invention is to provide a method and cryoprobethat will enable a precise localization of the cryotreatment.

A further objective of the invention is to provide a simplified andcompact apparatus for cryosurgery.

The present invention pertains to an apparatus for cryosurgery. Theapparatus comprises a cryoneedle having a diameter less than 3.2 mm. Theapparatus is also comprised of a thermal insulation shell disposed abouta portion of the cryoneedle for reduction of heat transfer fromsurrounding tissues or freezing prevention of surrounding tissues duringapplication of the cryoneedle with the shell. The cryoneedle and shellare configured for insertion into a body of a patient.

The present invention pertains to a method for freezing tissues. Themethod comprises the steps of inserting a cryoneedle having a diameterof less than 3.2 mm into a patient's body. Next, there is the step offlowing the cryofluid through the cryoneedle.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings, the preferred embodiment of the inventionand preferred methods of practicing the invention are illustrated inwhich:

FIG. 1 is a side view of the cryoprobe A of the invention.

FIG. 2 is a side view of the cryoprobe B of the invention.

FIG. 3 is a schematic view of the cryosurgical apparatus with a singlecryoprobe.

FIG. 4 is a schematic view of the cryosurgical apparatus with 3cryoprobes.

FIG. 5 is a diagrammatic representation showing some stages in cryoprobeinsertion and localization: FIG. 5.a insertion of cryoneedle 1 using animaging device and a localization technique (such as ultrasound andstereotactic localization technique, respectively); FIG. 5.b insertionof thermal insulation shell 4; FIG. 5.c completion of the cryoprobeassembly and connection to a pressurized cryofluid source.

FIG. 6 is a schematic representation of the construction of thecryoprobe tip: FIG. 6.a first the ends are cut at an angle φ; and thenFIG. 6.b the tube's tips are bent, one towards the other. Finally thetube's walls, 35 and 36, are welded together in a way that will allowfluid flow from one tube to the other.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to the drawings wherein like reference numerals refer tosimilar or identical parts throughout the several views, and morespecifically to FIGS. 1-4 thereof, there is shown an apparatus 100 forcryosurgery. The apparatus 100 comprises a cryoneedle 1 having adiameter less than 3.2 mm. The apparatus 100 is also comprised of athermal insulation shell 4 disposed about a portion of the cryoneedle 1for reduction of heat transfer from surrounding tissues, or freezingprevention of surrounding tissues, during application of the cryoneedle1 with the shell 4. The cryoneedle 1 and shell 4 are configured forcontact with and preferably insertion into a body of a patient.

Preferably, the cryoneedle 1 has a tip 33. Preferably, the tip 33 ispointed. Additionally, the apparatus 100 preferably includes aprotection tube 6 for protection of an operator's hand duringapplication of the cryoneedle 1. The shell 4 is disposed between theprotection tube 6 and the tip 33. The protection tube 6 is disposedabout the cryoneedle 1 and configured with the cryoneedle 1 and theshell 4 to be outside the body when the cryoneedle 1 and the shell 4 areinserted into the body of the patient during application. The protectiontube 6 and the shell 4 can be slidably attached to the cryoneedle 1 asis presented in FIG. 1. Alternatively, the insulation shell 4 can berigidly connected to the cryoneedle 1 as is presented in FIG. 2. Thecryoneedle 1 preferably has an inlet tube 35 through which cryofluidflows during application of the cryoneedle 1 to the tip 33 and an outlettube 36 through which cryofluid flows during application of thecryoneedle 1 from the tip 33. The outlet tube 36 preferably has a venttube 7 which releases the cryofluid to the environment. Preferably, thecryoneedle 1 has a bridging connector portion, such as unshaped channelconnector portion 34 disposed in conjunction with the tip 33 andconnected with the inlet tube 35 and the outlet tube 36 to connect theinlet tube 35 and the outlet tube 36 and to allow cryofluid to flow fromthe inlet tube 35 to engage the tip 33 and flow out to the outlet tube36. The inlet tube 35 preferably has an inside diameter between 0.8 mmand 2 mm. The outlet tube 36 preferably has an inside diameter between0.8 mm and 2 mm. Preferably, the inlet tube 35 is in parallel with theoutlet tube 36 and the inlet tube 35 is attached to the outlet tube 36.

The tip 33 is formed by taking two separate tubes and cutting their endsat an angle of about 15°, as shown in FIG. 6a. The cut angled ends arethen connected, for example, by being soldered or welded together toform the tip 33, as shown in FIG. 6b.

The apparatus 100 preferably includes a pressurized cryofluid sourcemechanism 30 connected to the inlet tube 35 via feeding tube 9 forproviding pressurized cryofluid to the inlet tube 35. The pressurizedcryofluid source mechanism 30 preferably includes a container 11 ofcryofluid connected to the feeding tube 9. The pressurized cryofluidsource mechanism 30 preferably also includes a tank 15 of pressurizedgas connected to the container 11 to pressurize the cryofluid in thecontainer 11. Additionally, the source mechanism 30 preferably includesa pump 31 connected to the tank 15 to pressurize the tank 15. The sourcemechanism 30 preferably also includes a control valve 10 disposed on thefeeding tube 9 to control the flow of cryofluid from the container 11.

Additionally, the apparatus 100 preferably includes a temperature sensormechanism 40 in contact with the cryoneedle 1 adjacent the tip 33 forsensing the active surface temperature of the cryoneedle 1. Thetemperature sensor mechanism 40 preferably includes a temperature sensor2 disposed adjacent the tip 33 and in contact with the cryoneedle 1. Thetemperature sensor mechanism 40 preferably also includes sensor wires 3connected to the sensor 2 and extending from the sensor 2. Furthermore,the temperature sensor mechanism 40 preferably includes a temperaturemeasurement unit 22 connected to the sensor wires 3 for identifying thetemperature sensed by the sensor 2.

The apparatus 100 can also include an imaging mechanism 44 for managingthe cryoneedle 1 as it penetrates into the body of a patient. Theapparatus 100 can also include at least a second cryoneedle 1 and asecond thermal insulation shell 4 disposed about a portion of the secondcryoneedle 1, as is presented in FIG. 4. The second cryoneedle 1 isconnected to the source mechanism 30.

The present invention pertains to a method for freezing tissues. Themethod comprises the steps of bringing into contact and preferablyinserting a cryoneedle 1 having a diameter of less than 3.2 mm with orinto a patient's body. Next, there is the step of flowing the cryofluidthrough the cryoneedle 1. Preferably, the cryofluid is vented to theenvironment.

Preferably, after the inserting step, there is the step of sliding aninsulation shell 4 in place over a predetermined portion of thecryoneedle 1 in the body of the patient. After the sliding step, thereis preferably the step of sliding a protection tube 6 in place over thecryoneedle 1 until it is adjacent to the shell 4. The protection tube 6is outside the patient's body. In an alternative preference, theinserting step includes the step of inserting the cryoneedle 1 with aninsulation shell 4 positioned about the cryoneedle 1 at a predeterminedlocation simultaneously into the body of the patient. Additionally, theinserting step preferably includes the step of imaging the cryoneedle 1as it is inserted into the patient's body.

In the operation of the preferred embodiment, an apparatus 100, whichhas a cryoprobe such as a cryoprobe A, as shown in FIG. 1, is comprisedof three main components: a cryoneedle 1, a thermal insulation shell 4,and a protection tube 6. The cryoprobe is assembled during, and as apart, of the cryosurgical procedure, as will be described in detailhereafter. Cryoneedle 1 has a U shape configuration and a sharp pointedtip 33, which is made of very fine tubes. Cryoneedle 1 leads thecryofluid forward, from feeding tube 9, through the inlet tube 35 ofcryoneedle 1, to the cryotreated region, and backward, through outlettube 36, to vent tube 7. Insulation shell 4 surrounds a part ofcryoneedle 1 to reduce heat transfer from the surrounding tissues to thecryoneedle. Insulation shell 4 contains thermal insulator 5. Protectiontube 6 surrounds an other part of cryoneedle 1, adjacent to insulationshell 4 but outside of the body, to protect the operator's hands and toreduce heat transfer from the surroundings to the cryoneedle. Insulationshell 4 as well as protection tube 6 are free to slide axially alongcryoneedle 1. Feeding tube 9 feeds cryoneedle 1 with pressurizedcryofluid, which is connected by fitting 8 to the inlet tube 35 ofcryoneedle 1. The cryofluid exits from cryoneedle 1 through flexiblevent tube 7, which is preferably connected under a pressure fitting.

The tubing from the coolant container 11 to fitting 8 is made ofstainless steel, but copper, brass, steel or any other metallic alloy issuitable. The stainless steel can guarantee flexibility in the cryogenictemperature range and a long life. Flexible metallic tubes have a uniqueconfiguration and are available for commercial usage. Some plastics arebrittle materials at cryogenic temperature range and therefore aregenerally not suitable for this task. The feeding tube 9 should beinsulated by vacuum in order to reduce heat losses between the coolantcontainer 11 and the cryoprobe. The simplest way of constructing aflexible and vacuum insulated tube is by using two standard flexibletubes, one inside the other. The space between the tubes is then sealedby sealing, for example, welding, while the air in between the tubes ispumped out to achieve a vacuum between the inner and outer tubes. Adiameter ratio of 1 to 2 between the inner and the outer flexible tubesis suitable.

The internal diameter of the inner flexible tube of the feeding tube 9should be about 3 times the inner diameter of the cryoneedle tubes, fora single cryoprobe operation. This ratio should be increased to about 5for a multi-cryoprobe operation. This large diameter of flexible tube ischosen to reduce pressure losses between the coolant container and thecryoprobe. It is noted that the heat losses from the feeding tube 9increase with the diameter.

Cryoprobe A can actually work without the protection tube 6, which doesnot affect significantly the performance of the apparatus. Protectiontube 6 is mainly used for safety reasons, to protect the cryosurgeon'shands. This tube should be made of a plastic material like Teflon orPlexiglass which have low thermal conductivities. Typical thermalconductivity value of plastics is about 0.1 W/m-° C.

The cooling process in cryoprobe A takes place as follows. Cryofluid isforced from a cryofluid source into the cryoprobe through feeding tube9. The cryofluid flows along cryoneedle 1 through the inlet tube 35towards the cryoneedle tip 33 and then backwards through outlet tube 36towards vent tube 7. Inside protection tube 6 and insulation shell 4, inboth flow directions, the heat transfer from the surroundings and fromthe surrounding tissues, respectively, is minimal. The only significantheat transfer occurs where cryoneedle 1 is in direct contact with thetissue, and therefore this area is designated herein as the cryoprobeactive surface. Downstream heat convection takes place along thecryoprobe active surface, with or without the boiling phenomenon insidethe cryoneedle, and causes freezing of the undesired tissues. Thetemperature of the cryoprobe active surface is monitored by temperaturesensor 2 and the signals are transferred through temperature sensorwires 3 to temperature measurement unit 22, as shown in FIG. 3.Monitoring of the temperature near the cryoprobe tip 33 is required forcontrolling the coolant (liquefied gas) flow rate. The temperature ofthe cryoprobe active surface, to which the temperature sensor isattached, is expected to be very close to the coolant boilingtemperature at extremely high flow rates. The temperature is notexpected to drop much while reducing the flow rate, until a certainpoint of which the boiling rate is higher than the flow rate and theflow of the liquefied coolant turns entirely into gas. The flow rate atwhich this phenomenon occurs is defined here as the critical flow rate;applying flow rates above the critical flow rate will result in a wasteof coolant while applying flow rates below the critical flow rate willresult in a significant reduction of the cooling power. Therefore, thetemperature sensor at the cryoprobe tip 33 acts as a flow rateindicator, telling the operator to increase or decrease the coolant flowrate via control valve 10. The usage of a thermocouple as a temperaturesensor 2 is convenient and inexpensive. The couples copper-constantan oriron-constantan are suitable for the cryogenic temperature range. Thetemperature measurement unit 22 is a standard unit that amplifies thethermocouple signal and translates them into temperature values. Thisunit should be able to operate between normal body temperature range,i.e. at least 40° C., down to the boiling temperature of the coolant,i.e. −196° C. for the liquid nitrogen case.

The cooling effect of the cryoneedle is achieved by a boiling phenomenoninside the cryoneedle's tubes. The boiling phenomenon, or liquid-gasphase change, takes place at a constant temperature and demands arelatively high energy, known as latent heat. For example, at a standardatmospheric pressure, nitrogen boils at −196° C. and demands an energyof 161 kJ per liter of liquid. The cooling process in the cryoneedletakes place as follows: the coolant enters the inlet tube of thecryoneedle at its liquid state; because of temperature differences, heatis transferred from the warm surrounding tissues through the cryoneedletubes' walls to the coolant. This heat transfer causes energy releasefrom the surrounding tissues, which lowers their temperature andessentially causes the formation of the ice-ball. On the other hand, thesame heat transfer causes energy absorption in the coolant, whichchanges the coolant phase from liquid to gas. More and more energy isabsorbed by the coolant as it flows, which continually contributes tothe coolant phase change process. In case of a high flow rate, relativeto the heat transfer from the surrounding tissue and the total length ofthe cryoneedle tubes, the coolant will not be transformed completelyinto gas inside the cryoprobe's tubes and therefore its balk temperaturewill be relatively close to the coolant boiling temperature. Atrelatively low flow rates, however, the phase change will be completedat some downstream point in the tubes, the boiling effect will vanishand the gas will warm up.

In general, liquid nitrogen is widely accepted as a coolant forcryosurgical applications since it has no side effects (79% of the airis nitrogen). Other cryogenic coolants may be used as well, such asliquefied air and liquefied helium, which boil at −178° C. and −267° C.,respectively.

Cryoprobe B configuration, as shown in FIG. 2, is similar to cryoprobe Awith the only exception that insulation shell 4 is rigidly connected tocryoneedle 1. Thermal insulation shell 4 contains thermal insulationmaterial 5 such as minerals, gas, or vacuum. However, the preferableinsulation technique is vacuum for both apparatus A and B. The coolingprocess in cryoprobes B is similar to that in cryoprobe A, as describedabove. All tubes' walls should be made as thin as possible. Usingstainless steel, a wall thickness of 0.1 mm should be sufficient.

Three typical dimensions characterize the cryoprobe: (1) the diameter ofthe cryoneedle's inlet and outlet tubes; (2) the diameter of the thermalinsulation; and (3) the length of the cryoprobe active surface. An outerdiameter of 1 mm is sufficient for both the cryoneedle's inlet andoutlet tubes, for some applications, in cases where stainless steeltubes with extra-thin walls are used (which have a wall thickness of 0.1mm). However, the longer dimension of the cryoneedle cross section willbe the sum of the diameters of the two adjacent tubes, i.e. 2 mm, inthis case.

An outer diameter of 3.2 mm is sufficient for the thermal insulationshell, for the above case. Taking in account the thermal insulation wallthickness, this configuration should leave about 0.5 mm clearance fromeach side of the cryoneedle, in the direction of the longer dimension ofthe cryoneedle cross section. This clearance will provide a sufficientspace for the vacuum to be effective as a thermal insulator.

It is noted that the 3.2 mm thermal insulation is not inserted all alongthe cryoneedle. Therefore, the cross section dimensions along the activecryoprobe surface are 1×2 mm, while along the thermal insulation thecryoprobe diameter is 3.2 mm. A cross section of 1×2 mm is about thesmallest cryoprobe cross section available at this time.

The cryoneedle should be made of stainless steel for the generalapplication of cryosurgery. However, for the special application of anMRI controlled cryosurgery, the cryoneedle should be made of copper orbrass which are compatible with the MRI environment. In this case, thecryoneedle should be gold coated to protect the cryotreated tissue.

Currently, there is only one main well known concept for the design andconstruction of a boiling effect based cryoprobe, which was invented byCooper at 1961. Cooper's approach is to place three tubes one inside theother, where the inner tube carries the coolant to the cryoprobe tip,the second tube carries the coolant gas back from the tip, and the spacebetween the latter tube and the most outer tube is used for vacuuminsulation.

The cryoprobe described herein has a very different configuration, whichis based on a unshaped cryoneedle. The cryoneedle comprises two adjuncttubes and not one inside the other. One form of the cryoprobe (cryoprobeA of the invention) is assembled during the cryoprocedure which allows aminimal destruction to the cryotreated tissue, due to cryoprobepenetration, and an accurate localization of the cryoprobe tip 33.

The term “cryoneedle” is used herein for the presentation of the presentinvention, however, one must not be confused between this particularcryoneedle and a simple needle which carries a cryo-fluid. An ordinaryneedle has an inlet on one end and an outlet on the other end. Thecryoneedle has the inlet in adjunct with its outlet, on the same endwhile the cryoprobe tip 33 is on the other end. The unique U-shapeconfiguration of the cryoneedle requires a special design andconstruction for this particular application.

The term cryoneedle appears in the literature for two other butdifferent applications: (1) for dermatology applications (Weshahy, A.H., 1993, “Interlesional Cryosurgery: A New Technique UsingCryoneedles”, J. Dermatol. Surg. Oncol., Vol. 19, pp. 123-126), where abanded needle is inserted through the skin and below a tumor. In thiscase, the cryoneedle is a simple needle which carries a cryofluid. (2)For an application on hemorrhoids (Gao, X. K., Sun, D. K., Sha, R. J.,Ding, Y. Sh., Yan, Q. Y., and Zhu, C. D., 1986, “Precooled,Spring-Driven Surgical Cryoneedle: A New Device forCryohaemorrhoidectomy”, Proceedings of the 11th International CryogenicEngineering Conference, IECE 11, Berlin, West Germany, pp. 825-829,incorporated by reference herein), where a pre-cooled needle is insertedinto an undesired tissue. The cryoneedle does not actually carry anycryofluid in the latter case.

One form of a pressurized cryofluid source is presented in FIG. 3. Thecryofluid is contained in a thermal insulated container 11. Container 11is pressurized by compressed air from air tank 15, through flexible airpressure pipe 13 and valve 14. Air tank 15 is pre-charged withcompressed air by an external pressure source like an electric pump 31.Air tank 15 is designed to have much larger volume than cryofluidcontainer 11. Therefore, the change in total gas volume during theentire cryosurgical operation is relatively small and is approximatelythe volume ratio of cryofluid container 11 to air tank 15. Underisothermal conditions, the total air pressure decrease will beproportional to the above volume ratio. However, this is not exactly thecase since the air which enters container 11 contracts due totemperature decrease and therefore contributes to the overall pressuredrop. Pressure decreases are compensated for by high pressure air tank20. High pressure air tank 20 is connected to air tank 15, through pipe19 and pressure regulator 18. Pressure regulator 18 keeps the pressurein air tank 15 on some set point. By analogy between fluid pressure andelectrical potential, the setup of air tanks 15 and 20 can be viewed asa “pressure battery”. The usage of air tank 20 is optional but notnecessary. It is needed only when the volume ratio of air tank 15 tocontainer 11 is not large enough, or in cases where a very accuratepressure control is required. The “pressure battery” may include theelectric pump 31, or may be pre-charged by an external source.

Contrary to practice, the pressurized coolant system of the apparatus,as presented above, is separated into two main components: the coolantcontainer 11 and the “pressure battery”. This set-up has the followingadvantages: (1) the larger part of the system—the pressure battery—canbe moved far from the cryosurgeon, possibly to another room, thusleaving more space in the operating room; (2) the coolant container isplaced very close to the cryotreated tissue which reduces undesiredcoolant boiling along the feeding pipes. This reduces both the coolantconsumption and the working pressure required to force the coolantthrough the feeding pipe. In turn, the reduction of the coolantconsumption reduces the volume of the coolant container. Ordinarycryosurgery systems include the pressurized system and the coolantcontainer in one unit.

Any ordinary air compressor could serve as an air pressure source forthe cryofluid container 11. However, the air pressure system aspresented here has advantages as a part of a surgical apparatus in thatit can be very light in weight, small in dimension, very quiet inoperation, and independent in power supply.

Practically, feeding tube 9 has to be as short as possible and thereforecontainer 11 should be placed as close as possible to the cryotreatedtissues. This can be compensated by a long air pressure pipe 13. Thisarrangement will decrease the heat losses along feeding tube 9 to thesurroundings, which will decrease the required cryofluid flow rate, andwhich in turn will decrease the required volume of cryofluid container11 for a specific operation. Low flow rates and short feeding tubes willrequire lower working pressures in the air pressure system. Furthermore,a smaller cryofluid container will require a smaller air tank volume.Moreover, the closer the cryofluid container is to the cryotreatedtissues, the more compact apparatus 100 becomes in regard to dimensionsand the safer the apparatus becomes in terms of pressure. One liter ofcoolant is generally needed for a triple cryoprobe operation, for aduration of 15 minutes under a pressure of 30 psi. A 2-liter vacuuminsulated coolant container, a 34-liter low air pressure tank and a22-liter high pressure air tank were used with the apparatus 100.However, the high pressure air tank was not needed for a single usage ofthe coolant container due to the high volume ratio of the low pressureair tank to the coolant container, as described above.

Before commencing the cryosurgery, the cryosurgeon will typically studythe location, depth and configuration of the undesired tissues. Thecryosurgeon will study the surrounding healthy tissues as well, andespecially the vital tissues. This study can be performed viaultrasound, CT or MR imaging techniques. Based on this study, one ormore appropriately configured cryoprobes will be chosen.

A schematic view of the cryosurgical apparatus with 3 cryoprobes isshown in FIG. 4. The pressurized coolant source remains in the sameconfiguration as for a single cryoprobe operation, as presented above.For a multi-cryoprobe, parallel feeding tubes lead the coolant to thecryoprobe and the temperature is monitored at the tip 33 of eachcryoprobe separately. Each cryoprobe has a temperature sensor and acontrol valve on its feeding tube 9 in a multi-cryoprobe operation. Allthe cryoprobes flow rates are operated at the same technique presentedabove, at the beginning of the cryoprocedure. As cryosurgery proceeds, aneed to reduce the cooling power of one or more cryoprobes may arise dueto the presence of vital organs around the cryotreated tissue, or due toan irregularity in shape of the cryotreated tissue (tumor). At thisstage, the cryosurgeon compares the frozen region formation with thecryotreated tissue shape via an imaging device such as ultrasound andoperates the control valves accordingly.

The method of operation of cryoprobe A is addressed first. Utilizing aneedle localization technique or a stereotactic localization technique,cryoneedle 1 will be inserted into the undesired tissue, as shown inFIG. 5a and as described hereafter. The fine diameter of the cryoneedleand its sharp pointed tip 33 are suitable for a straightforwardinsertion, without any cutting. The cryoneedle insertion procedure willbe repeated in case of a multi-cryoprobe operation. Cryoneedles can berelocated at this stage with no significant damage to surroundingtissues.

The insertion of insulation shell 4 is next. Insulation shell 4 will beslide along cryoneedle 1 and will be inserted into the tissue, FIG. 5b.A small incision in the skin may be needed for the insertion of tube 4.The insertion of insulation tube 4 will be monitored by an imagingtechnique, to leave the appropriate cryoprobe active surface near thetip 33 of the cryoneedle. The other end of the insulation shell willremain outside of the body. The length of the insulation shell will bechosen for a particular cryotreatment according to the length of thecryoneedle, the depth of the undesired tissues, and the requiredcryoprobe active surface. Insertion of the insulation shell will berepeated in case of multi-cryoprobe operation.

Protection tube 6 will then be placed along cryoneedle 1, adjacent toinsulation shell 4, FIG. 5c. Flexible vent tube 7 will be connected tothe cryoneedle under a pressure fit. The length of protection tube 6will be chosen to fit between insulation shell 4 and vent tube 7.Lastly, the inlet tube 35 of cryoneedle 1 will be connected to feedingtube 9 and the cryoprobe will be ready for operation. Container 11 willbe filled with cryofluid and air tanks 15 and 20 will be charged withcompressed air in advance.

The freezing stage is then started. While monitoring the frozen regionformation, the cryosurgeon will operate the cryoprobe by means of valve10. In case of a multi-cryoprobe operation, each cryoprobe will becontrolled independently. The freezing process will continue until theentire target region is frozen, or until a danger of cryodestruction tosurrounding tissues appears. Control valve 10 should be a standardneedle valve which is designed for cryogenic temperatures. These valvesare available in a wide range for commercial usage.

The thawing stage is then started. Thawing can be performed by eithernatural thawing, i.e. leaving the tissue to be thawed due to bloodperfusion and metabolic activities, or by forcing warm fluid through thecryoprobe passageway, i.e. disconnecting the cryoneedle from feedingtube 9 and re-connecting it to a pressurized warm fluid source.

The cryoprobe(s) can now be cooled again, in case of repeatedfreezing/thawing cycles cryotreatment.

The method of operation of cryoprobe B is addressed next. The method ofoperation of cryoprobe B is similar to the method presented above forcryoprobe A with the only exception that cryoneedle 1 and thermalinsulation shell 4 are inserted and extracted from the body together, asa one unit. This operation is suitable for cases in which the outerdiameter of thermal insulation shell 4 is relatively small.

Any minimal-invasive cryoprocedure has to rely on an imaging techniquesuch as ultrasound, CT or MRI. The ultrasound is widely accepted bycryosurgeons. The imaging technique is desired for two different tasks:(1) the localization of the cryoneedle(s), and (2) monitoring thecryolesion growth (the freezing front propagation). The uniqueness ofthe cryoneedle configuration of the invention, as being assembled duringthe cryoprocedure and/or as having small dimensions, offers a majoradvantage for an easy and precise localization of the tip 33. Twocryoneedle localization techniques are discussed below: needlelocalization and stereotactic.

Needle localization technique: This technique is currently used forguidance of the surgeon to the tumor, and towards the extraction of atumor of the breast, as follows. First, the tumor is located on theultrasound image. Then, monitored by the ultrasound, a needle isinserted into the center of the tumor (while the patient is treated witha local anaesthesia). Lastly, the patient is transferred to theoperation room and a surgery is performed to extract the tumor. Thetumor is found by dissecting along the needle.

Localization of a standard cryoprobe by means of the needle localizationtechnique should be performed as described above, where a pathway forthe cryoneedle is dissected along the needle.

Localization of the cryoneedle of the invention by means of the needlelocalization technique is performed in one of the two alternative ways:(1) By using the cryoneedle as the needle for the needle localizationprocedure. (2) First by inserting the standard needle, and then byreplacing it with the cryoneedle. In both cases, a pathway is not neededfor the cryoneedle, however, a small incision may be required on theskin. The apparatus will be assembled after the localization of thecryoneedle, in situ, as described above.

Stereotactic localization technique: The cryoneedle is guided to thetumor by stereotactic technique. This requires the use of a stereotacticbreast imaging/biopsy table which provides digital mammographic imagesof the breast. The cryoneedle is mounted on a needle holder which ismounted on the stereotactic table. Using computer generated coordinatesobtained from a stereo images, the biopsy needle or cryoneedle ispositioned into the tumor and therapy is carried out. This can beperformed under a local anaesthesia. In this case, the cryoneedle has tobe designed to be compatible, in size and shape, with the standardbiopsy needle used with the stereotactic device. The apparatus will thenbe assembled, in situ, as described above.

Although the invention has been described in detail in the foregoingembodiments for the purpose of illustration, it is to be understood thatsuch detail is solely for that purpose and that variations can be madetherein by those skilled in the art without departing from the spiritand scope of the invention except as it may be described by thefollowing claims.

What is claimed is:
 1. A method for freezing tissues comprising thesteps of: inserting a cryoneedle having a diameter of less than 5 mminto a patient's body, the cryoneedle has a sharp pointed tip, an inlettube and an outlet tube disposed alongside the inlet tube, and au-shaped channel connector connected to the inlet tube and the outlettube through which cryofluid from the inlet tube flows to the outlettube; sliding an insulation shell in place over a predetermined portionof the cryoneedle in the body of the patient; and flowing cryofluid intothe inlet tube, through the channel connector and out of the cryoneedlethrough the outlet tube.
 2. A method as described in claim 1 wherein theflowing step includes the step of flowing cryofluid through thecryoneedle and venting the cryofluid into the environment.
 3. A methodas described in claim 2 including after the sliding step, there is thestep of sliding a protection tube in place over the cryoneedle until itis adjacent to the shell but the protection tube is outside thepatient's body.
 4. A method as described in claim 3 wherein the flowingstep includes the step of flowing the cryofluid out of the cryoneedle toa vent connected to the outlet tube.
 5. A method as described in claim 4including the step of sensing the temperature of the cryoneedle with atemperature sensor disposed adjacent the tip and in contact with thecryoneedle.
 6. A method as described in claim 5 wherein the insertingstep includes the step of inserting the cryoneedle which is made ofcopper or brass and is gold coated.
 7. A method as described in claim 2wherein the inserting step includes the step of inserting the cryoneedlewith an insulation shell positioned about the cryoneedle at apredetermined location simultaneously into the body of the patient.
 8. Amethod as described in claim 2 wherein the inserting step includes thestep of imaging the cryoneedle as it is inserted into the patient'sbody.
 9. A method as described in claim 4 including the step of sensingthe temperature of the cryoneedle with a temperature sensor disposedadjacent the tip and in contact with the cryoneedle.
 10. A method asdescribed in claim 9 wherein the inserting step includes the step ofinserting the cryoneedle which is made of copper or brass and is goldcoated.
 11. A method for freezing breast tissue of a patient comprisingthe steps of: forming images of the breast of the patient; generatingwith a computer aided coordinates to position a cryoprobe having acryoneedle having a diameter of less than 5 mm in the breast of thepatient, the cryoneedle has a sharp pointed tip, an inlet tube and anoutlet tube disposed alongside the inlet tube, and a u-shaped channelconnector connected to the inlet tube and the outlet tube through whichcryofluid from the inlet tube flows to the outlet tube; guiding thecryoprobe into the breast of the patient based on how the cryoprobeappears in the images and the computer aided coordinates; sliding aninsulation shell in place over a predetermined portion of a cryoneedlein the body of the patient; and flowing cryofluid into the inlet tube,through the channel connector and out of the cryoneedle through theoutlet tube.
 12. A method as described in claim 11 wherein the formingstep includes the step of forming stereotactic images of the breast ofthe patient.
 13. A method as described in claim 12 wherein the guidingstep includes the step of placing the cryoprobe into a needle holder,and guiding the cryoprobe along the needle holder into the patient. 14.A method as described in claim 13 including after the guiding step,there is the step of monitoring cryolesion growth.